W6304-ZZ bearing: complete specifications & equivalents
The W6304-ZZ is a ISO 15 radial bearing sized 20 x 52 x 15 mm (bore x OD x width) with ZZ sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 20 mm |
| Outer diameter D | 52 mm |
| Width B | 15 mm |
| Material | SS440C |
| Seal / shield | ZZ |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 13.8 kN |
| Basic static load rating C0 | 7.8 kN |
| Fatigue load limit Pu | 0.335 kN |
| Reference speed (thermal) | 34000 rpm |
| Limiting speed (mechanical) | 17000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 144 g |
| Manufacturer designation | W 6304-2Z |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & 6300-series range
| Bore d | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.591 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 16 mm |
| Smallest bore in 6300-series | 2 mm |
| Largest outer diameter in 6300-series | 500 mm |
| Width range across 6300-series | 3–95 mm |
| Bore position in 6300-series (smallest first) | 9 of 40 |
| Bore above smallest 6300-series size | 18 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| W6304-2RS | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×52×15 mm envelope and equivalent catalogue ratings; W 6304-2RS1 is the two contact elastomer seals execution of this size — boundary dimensions interchangeable, only the seal/shield/cage execution differs. |
| W6304 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 20×52×15 mm envelope and equivalent catalogue ratings; W 6304 is the open arrangement execution of this size — boundary dimensions interchangeable, only the seal/shield/cage execution differs. |
| 6304 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6304 shares the 20×52×15 mm envelope but carries different catalogue ratings (13.8/7.8 kN vs 16.8/7.8 kN) — the stainless execution is not a load-rating equivalent. |
| 6304-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6304-2Z shares the 20×52×15 mm envelope but carries different catalogue ratings (13.8/7.8 kN vs 16.8/7.8 kN) — the stainless execution is not a load-rating equivalent. |
| 6304-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6304-2RSH shares the 20×52×15 mm envelope but carries different catalogue ratings (13.8/7.8 kN vs 16.8/7.8 kN) — the stainless execution is not a load-rating equivalent. |
| 6304-RSR | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6304-2RSL shares the 20×52×15 mm envelope but carries different catalogue ratings (13.8/7.8 kN vs 15.9/7.8 kN) — the stainless execution is not a load-rating equivalent. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the W6304-ZZ model number is decoded
The W prefix denotes SKF stainless steel deep-groove bearings (X108CrMo17 / AISI 440C class rings). In the 6300-series, the last two digits encode the bore: 6304 carries code 04 = 20 mm (code × 5). Envelope 20×52×15 mm (0.787×2.047×0.591 in), C 13.8 kN, C0 7.8 kN, Pu 0.335 kN; limiting speed 17000 r/min and mass 144 g. SKF spells the double shield W 6304-2Z (suffix 2Z); the shields are non-contact, retain grease and block coarse debris but are not liquid-tight. Stainless is chosen for corrosion and washdown duty, not for extra load — the same-envelope chrome-steel bearing rates higher.
Typical equipment & failure modes
Common applications
- appliances exposed to moisture
- food and beverage conveyors
- pharmaceutical and packaging machines
- washdown-duty equipment
Known failure patterns
- surface staining and pitting when even the stainless steel is left unlubricated in salty or acidic duty
- seal and grease failure before the rings corrode in sustained washdown service
- fine-particle abrasion when non-contact shields let dust through in a dirty environment
- grease aging inside the shielded cavity with no relubrication path
Selection pitfalls — read before you substitute
- Stainless bearings carry lower load ratings than chrome steel of the same envelope: W6304-ZZ is quoted at C 13.8 kN versus the 15 mm-wide 52100 version — do not swap on dimensions alone.
- Food, pharmaceutical and washdown positions need food-grade grease (e.g. NSF H1 registered) inside W6304-ZZ; standard fill is industrial grease unless specified otherwise.
- Corrosion resistance depends on clean, undamaged surfaces: never weld near W6304-ZZ or scratch the raceways during mounting, since the damaged spot starts corrosion.
- Temperatures above roughly 300 °C temper the stainless races; even standard greases fail far earlier — keep W6304-ZZ inside the quoted grease temperature range.
- The fatigue load limit is 0.335 kN; it feeds the equivalent-mean-load check, not the basic life calculation — do not substitute one for the other.
- Fillet radii must clear the W6304-ZZ chamfer so the 15 mm-wide ring seats square; an oversized shaft radius creates point contact on the ring face.
Frequently asked questions
What are the dimensions of the stainless W6304-ZZ?
SKF W 6304-2Z measures 20×52×15 mm (0.787×2.047×0.591 in), about 144 g, C 13.8 kN.
What does the W in W 6304-2Z mean?
W is the SKF prefix for stainless steel deep-groove bearings (rings in X108CrMo17 / AISI 440C class); the rest of the designation follows the normal series and bore rules.
Can I replace a chrome-steel bearing with stainless W6304-ZZ?
The envelope matches, but stainless rates lower (C 13.8 kN for W 6304-2Z); for corrosive environments that trade-off is intended, for high loads it shortens life.
Is the stainless bearing magnetic?
Yes. Bearing stainless steels are martensitic (hardened) and magnetic; non-magnetic austenitic grades cannot be hardened enough for raceways and balls.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-27. Read our editorial & correction policy.